Cam.



H. HARTT.

0AM. I APPLICATION FILED APR. 16, 1907.

91 6,702. Patented Mar. 30, 1909.

Hal.

WiTnesses: I I lrwmTbr:

v a I 2m 1 By PATENT OFFICE.

HENRY HA RTT, OF CHICAGO, ILLINOIS.

CAM.

Specification of Letters Patent.

Patented March 30, 1909..

Application filed April 15, 1907. Serial No. 368,284.

zen of the United States of America, and a resident of Chicago, county of Cook, and State of Illinois, have invented. certain new and useful Improvements in Cams, of which the following is a specification.

My invention relates to cams and has for itsobject improvements in the same. In the accompanying drawings-Figure 1 is an elevation of an ordinary grooved cam operating upon a rock-arm; Fig. 2 is a section on line 2-2 of Fig. 1 showin the construcion of the cam groove and rolls; Fig. 3 shows theordinary method of milling the oove of a cam, the purpose of which is to ustrate one of the defects which Lovercome; and Fig. 4v is the method which I employ of making the out which is defective in the ordinary process.

In the said drawings A is an ordinary rotating body moving in the direction of the arrow of Fig. 1, and having a cam-groove B in which operates the roll It on the rock arm 0. The real object of my invention will be better understood by a preliminary discussion of the defects of the devices of Fig. 1 asordinarily madeL In machinery requiring a comparatively high degree of accuracy, cam-grooves like B of Fig. 1- are milled by a templetso that both faces are finished, and theroll R is a comparativelyclose fit in the groove. With the cam moving in the directionof the arrow the strain is along the curve B. Owing to the rolling action there is comparatively little wear along the curve B but when the point B arrives at the roll R the said roll is thrown from the outer surface of the camstriking the groove to the inner surface,

The force of inner surface at the point B.

I this blow depends upon the abruptness of the change in the curve of the cam, the speed at which the cam moves, and the weight which is driven by the vibrations of the roll R. This causes a wear to occur at the g n B and at similar points adjacent to eac re- For various practical reasons rolls are made comparatively heavy and the reversal of their rotation is not instantaneous, and the result is that the surface of the roll rubs and grinds at the point B. The amount ofthis grinding action de ends largely upon the velocity with which t e roll R rotates and this increases with the radius of the camgroove. At the oint B the grinding action is greater and tie pounding action is less than at B As a result of these actions camgrooves and rolls soon lose the accuracy of their fits, and when wear is once fairly started it grows with increasing rapidity. I overcome this pounding action and the grinding.

action due to the reversal of the roll rotation by the construction shown in Fig. 2. In this case the rock-arm C carries two rolls R. and

R which are preferably of different diameters, and the groove surfaces A and A are on different lanes to match the rolls R and R The roll lt preferably rotates upon: a fixed sleeve or bushing D secured to a hub C formed solid with the rock-arm C. The roll R rotates upon a pin E and may or-may not have a loose bushing F. The ob'eot of the boss or hub C is sothat the pin will not have too great an overhangfrom the arm C, and the object of the sleeve or bushing D is to prevent Wear on the hub 0 When wear oc ours on the bushing D it may be removed and another substituted without requiring a new rock-arm, which would be the case if wear occurred direct y upon the hub C.

In cutting ordinary ca'rngrooves, the

rough casting is secured in position and the travel of the rotary cutter with respect thereto is determined by a previously constructed templet. The manner in which a cutter K cuts one of these cam-grooves is illustrated in Fig. 3. It is a well known principle in mechanics that for a cutter to leave a finely finished surface the cutter must cut against the feed. To cut with the feed causes the cutter to chatter and leave a wavy or uneven cutter, causing the surface H to also be uneven. y

, When cams are cut according'to my i'nve'n: tion, I cut the surface A (Figs. 2 and e) first,

the cutter being guided by the ordinary temthe surface A to be a telnplet for cutting the surface A When thus made, both surfaces are more even and finely finished than they are when out in the ordinary method. When a rolloperates alternately on opnosite sides of a cam-groove, the roll must beloose in the groove so that when it operates on one side it will not rub or touchthe other side.

wear, and wear progresses in proportion to the amount oflooseness. .Vvhen each surface has its independent roll, shown in Fig. 2, these rolls may fit snuglyenough to cause each roll to be in rolling contact with its respective surface at all times- This removes the pounding action before mentioned and leaves only variations of pressure at different points on the cam curve. It also removes the grinding action due to reversing the rotation ofthe roll two or more times for each rotation of the cam.

What I claim is i v 1. The combination With a cam providing two cam surfaces, and a body provided with a hub andarranged to be moved by said cam,

This. I preliminary looseness is the starting point of of a roller mounted upon said hub and so 10- cated as to engage one cam surface, a pin extending centrally through said hub, and a second roller mounted upon said pin and so located as to engage the other cam surface.

2. Thecombination with a cam providing two cam surfaces, and a body (provided with hub and arranged to be move by said cam,

of a sleeve fixed upon said hub, ,a cam-rollermounted to rotate upon said sleeve, a pinpassing centrz'i-lly through said hub, and a second cam roller mounted upon send pm, saidrollers being arranged so as to each act solely upon one cam surface, substantially as described.

3. The combinatlon with a cam providing two earn surfaces, an arm to be moved by said cam, and a pin extending through a hub on said arm, of two rollers mounted upon a common axis, one of said rollers being mount ed on said hub and the other roller mounted upon said pin.

4 The combination with ac'am having the faces of its groove 1n different planes, a body to be moved-by said cam, and a pin secured to said body, of vindependently rotatable rollers, one for each surface, one of the rollers being mounted upon a hub integral with the body tobe moved and the other roller mounted upon said pin.

Si ned at Chicago, 111., 4th day of Apri 1907.

HENRY HARTT.

Witnesses:

CAsPER' L. REDFIELD, CARRIE E. JORDAN. 

